In this talk, I will review the main highlights obtained in the context of the YSO GRAVITY GTO program, including results from statistical studies of the inner dusty disks, detailed constraints on the gaseous component at the star/inner disk scale and evidence for inner disk structure. Pioneering results from image reconstruction and time monitoring studies will be also presented. The power of combined GRAVITY/MATISSE and GRAVITY/SPIROU analysis will be illustrated in a few examples. These results will be put in context of the most recent numerical modeling of the star inner disk systems. Finally, I will present promising prospects for GRAVITY+ in synergy with future/existing instrumentation like JWST and ELT instruments.